ACL system for user permissions in Redis

Introduction

An ACL system helps control who can do what in a database. It keeps data safe by giving permissions only to the right users.

When you want to let some users read data but not change it.

When you need to stop unauthorized users from deleting important information.

When different users have different roles, like admin or guest.

When you want to track who can run certain commands in Redis.

When you want to quickly change user permissions without restarting Redis.

Syntax

Redis

ACL SETUSER username [rule [rule ...]]
ACL DELUSER username
ACL LIST
ACL GETUSER username

ACL SETUSER creates or updates a user with specific permissions.

Rules include commands allowed (+), commands denied (-), keys allowed (~), and passwords (>).

Examples

Creates user 'alice' who can run GET and SET commands on all keys, with password 'password123'.

Redis

ACL SETUSER alice on >password123 +get +set ~*

User 'guest' can only run GET on keys starting with 'public:', cannot run SET or DEL.

Redis

ACL SETUSER guest on +get ~public:* -set -del

Deletes the user 'guest' from the ACL system.

Redis

ACL DELUSER guest

Shows all users and their permissions.

Redis

ACL LIST

Sample Program

This creates a user 'bob' with password 'bobpass'. Bob can run GET and SET commands only on keys starting with 'data:'. Then it shows Bob's permissions.

Redis

ACL SETUSER bob on >bobpass +get +set ~data:*
ACL GETUSER bob

Important Notes

Always set strong passwords for users to keep your data safe.

Use ACL LIST to review all users and their permissions regularly.

Remember that permissions are additive; if you deny a command explicitly, it overrides allowed commands.

Summary

ACL controls who can do what in Redis.

Use ACL SETUSER to create or update users with specific permissions.

Check permissions with ACL GETUSER and list all users with ACL LIST.

Practice

1. What is the main purpose of Redis ACL (Access Control List)?

easy

A. To speed up Redis database queries

B. To control which users can perform specific commands and access keys

C. To backup Redis data automatically

D. To monitor Redis server performance

Solution

1. Step 1: Understand ACL purpose

   ACL in Redis is designed to manage user permissions, controlling what commands and keys users can access.

2. Step 2: Compare options

   Options B, C, and D describe unrelated Redis features like performance and backup, not ACL.

3. Final Answer:

   To control which users can perform specific commands and access keys -> Option B

4. Quick Check:

   ACL controls permissions = A [OK]

Hint: ACL is about permissions, not performance or backups [OK]

Common Mistakes:

• Confusing ACL with performance tuning
• Thinking ACL manages backups
• Assuming ACL monitors server stats

2. Which of the following is the correct Redis command to create or update a user with specific permissions?

easy

A. ACL CREATEUSER username on >password ~keys +commands

B. ACL UPDATEUSER username on >password ~keys +commands

C. ACL ADDUSER username on >password ~keys +commands

D. ACL SETUSER username on >password ~keys +commands

Solution

1. Step 1: Recall Redis ACL command syntax

   The correct command to create or update a user is ACL SETUSER followed by username and permissions.

2. Step 2: Check options

   Only ACL SETUSER username on >password ~keys +commands uses ACL SETUSER. Others use invalid commands like CREATEUSER, ADDUSER, UPDATEUSER which do not exist in Redis ACL.

3. Final Answer:

   ACL SETUSER username on >password ~keys +commands -> Option D

4. Quick Check:

   Use ACL SETUSER to set permissions [OK]

Hint: Remember: ACL SETUSER sets or updates users [OK]

Common Mistakes:

• Using non-existent ACL commands like CREATEUSER
• Confusing SETUSER with other verbs
• Missing required syntax parts like 'on' or '>'

3. Given the command ACL SETUSER alice on >mypassword ~cache:* +get +set, what permissions does user 'alice' have?

medium

A. User 'alice' is disabled and cannot run any commands

B. User 'alice' can run all commands on all keys

C. User 'alice' can only run GET and SET commands on keys starting with 'cache:'

D. User 'alice' can run GET and SET commands on all keys

Solution

1. Step 1: Analyze ACL SETUSER command parts

   'on' enables the user, '>mypassword' sets password, '~cache:*' limits keys to those starting with 'cache:', '+get +set' allows only GET and SET commands.

2. Step 2: Interpret permissions

   User 'alice' can only run GET and SET commands on keys matching 'cache:*'. Other commands or keys are denied.

3. Final Answer:

   User 'alice' can only run GET and SET commands on keys starting with 'cache:' -> Option C

4. Quick Check:

   Commands + keys limited = A [OK]

Hint: Check '+' for commands and '~' for key patterns [OK]

Common Mistakes:

• Assuming all commands are allowed
• Ignoring key pattern restrictions
• Thinking user is disabled without 'off'

4. You run ACL SETUSER bob on >secret +@all but Bob still cannot execute commands. What is the likely problem?

medium

A. Bob's client did not authenticate with the password

B. Bob's password was not set correctly

C. The command '+@all' is invalid syntax

D. Bob's user is disabled because 'on' was not set

Solution

1. Step 1: Check user status and permissions

   'on' enables Bob, '+@all' grants all command categories, and '>secret' sets password correctly.

2. Step 2: Identify why commands fail

   If Bob cannot run commands, likely he did not authenticate with the password, so Redis denies access despite permissions.

3. Final Answer:

   Bob's client did not authenticate with the password -> Option A

4. Quick Check:

   Authentication required after ACL SETUSER [OK]

Hint: Set password and authenticate client to enable commands [OK]

Common Mistakes:

• Forgetting to authenticate after setting password
• Assuming 'on' disables user if missing
• Thinking '+@all' is invalid

5. You want to create a Redis user 'reporter' who can only run the INFO command and read keys starting with stats:. Which command correctly sets this up?

hard

A. ACL SETUSER reporter on >pass123 ~stats:* +info

B. ACL SETUSER reporter on >pass123 ~stats:* +@read

C. ACL SETUSER reporter on >pass123 ~stats:* +get +info

D. ACL SETUSER reporter on >pass123 ~stats:* +get

Solution

1. Step 1: Understand command requirements

   User 'reporter' needs only the INFO command and access to keys starting with 'stats:'.

2. Step 2: Evaluate options

   ACL SETUSER reporter on >pass123 ~stats:* +info: ACL SETUSER reporter on >pass123 ~stats:* +info grants only the INFO command on keys starting with 'stats:'. ACL SETUSER reporter on >pass123 ~stats:* +get +info incorrectly grants +get which is not required. ACL SETUSER reporter on >pass123 ~stats:* +@read grants all read commands (+@read), which is too broad. ACL SETUSER reporter on >pass123 ~stats:* +get misses +info, so cannot run INFO command.

3. Final Answer:

   ACL SETUSER reporter on >pass123 ~stats:* +info -> Option A

4. Quick Check:

   Only INFO command + key permissions = C [OK]

Hint: Grant only needed commands with '+' and keys with '~' [OK]

Common Mistakes:

• Granting command categories instead of specific commands
• Missing +info for INFO command
• Forgetting to enable user with 'on'